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A simple pendulum of time period 1s and length l is hung from a fixed support at O, such that the bob is at a distance H vertically above A on the ground. The amplitude is θo. The string snaps at θ = θ0/2. Find the time taken by the bob to hit the ground. Also, find the distance from A where bob hits the ground. Assume θ0 to be small so that sin θo, θo and cos θ0 1.

Answer:

At t = t1 and θ= θ0/a

We have, T = 1 sec

θ0/2 = θ0 cos 2π/T t1

d θ/dt = – θ0 2π sin 2πt

At t = 1/6, that is when θ = θ0/2

d θ/dt = – θ0π√3

v/l = – θ0π√3

v = -θ0π√3l

θ0l [1/2 – π√6H/g] gives us the distance between the bob from A.